The operation of lithographic printing presses involves an interaction of water and ink and the inking system of the lithographic printing presses has not changed to any appreciable degree since the invention of the offset lithographic press in the early twentieth century.
My co-pending U.S. patent application Ser. No. 11/514,002, filed Aug. 30, 2006, relates to an offset lithography press and method for improving the performance of an offset lithography press wherein misting is virtually eliminated even at very high operational speeds.
While the invention disclosed in the above-identified application effectively solves misting problems, conventional offset lithography presses have another drawback relating to the dampening systems employed.
On a conventional lithographic offset press the rotating plate cylinder directly receives from a dampening unit engaging the plate cylinder a thin water layer that adheres to a non-printing surface such as an aluminum surface. The ink rollers of the press will deposit ink only where an impression or image layer, typically a polymer layer, has been applied to create a printing area. The non-printing area with the wafer-thin moisture layer refuses to take on ink.
As the plate cylinder rolls into contact with the adjacent blanket cylinder of a lithographic offset press, the ink is transferred to a blanket cylinder. Typically, the blanket cylinder is formed of steel and includes a rubber layer covering the steel. The blanket cylinder is in contact with an impression cylinder, typically formed of steel, which carries the paper receiving the ink from the blanket cylinder.
In the prior art systems described above, moisture directly applied to the plate by a dampening unit will evaporate as the plate cylinder passes in engagement with the inking rollers, and by the time contact is made with the blanket cylinder, the moisture has essentially disappeared. When the blanket cylinder contacts the paper it is almost dry and the paper wants to adhere to the blanket cylinder. The paper has a difficult time separating from the blanket cylinder and it is very noisy when separation occurs. In many instances the paper or particles thereof stick to the blanket cylinder to a sufficient degree to cause serious problems.